V6 strange (?) rendering behaviour

I’ve just purchased a new Mac mini to use V6 rhino on. When it comes to rendering, it seems to exhibit some odd behaviour. Before the purchase I was aware that the rendering ability would be poor.

When it starts a render, the CPU runs at around 85%. Around 2/3 of the way through (image area not time) the CPU speed halves, at 5/6 of the way through the speed again halves. It takes about 10 times as long to do the last 1/3 as it did the first 2/3. On one occasion it became so glacial (it was still going) I had to kill it.

My other observation is that the GPU was doing nothing during the whole process. I really don’t know enough about this to know if this is as should be expected, or I need to change some settings somewhere. The on board graphics is supposed to be the limiting factor, but they only seem to do any work during a render if I move something around on a screen.

If someone could point me towards a guide that would point the way, or if someone with experience in this area could give me a few pointers or just say that that’s as good as it’s going to get, I would be grateful.

I rarely do renders, but some times people seem more able to understand the part rendered with materials, texture and shading, rather than just a screen grab. So it comes in handy on odd occasions.

It should. Rhino 6 uses the CPU to render.


Pascal, thanks for the swift response.

I thought I’d read on the forum about the limitations of the Mac mini being the onboard graphics, just had a quick look, but couldn’t find it.

The change in speed I mention at the beginning of the post, does that make any sense?


Well, it does kind of make sense from back when I used a CPU renderer. The render job gets divided into ‘buckets’ that are each given to a CPU core, and as the buckets get used up and then there are fewer buckets left than cores, it slows down a lot until finally the last little chunk(which would very likely be the most difficult part of the whole scene) takes forever on one core. Making each ‘bucket’ smaller helps this, but then bigger ones render more efficiently so it’s a trade-off.

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My brand new MacBook Air 2019 with 16 MB RAM is getting extremely hot after a couple of simple 2500x1500 pixel renderings and the render speed goes down to 10% until I give it a break and let it cool down. Also after rendering a couple of files, even the displayed ‘rendered’ window mode stops showing the shaders accordingly … very annoying! Never had these kind of issues with my 7 year old MacBook Air mid 2013 with 8MB RAM and Rhino for Windows 7!

If it gets really hot it sounds cooling isn’t working properly.

Massive throttling is what I remember about a review of the 2019 Air, any sort of workload will just kill it, so badly that the older model is faster maybe.

I recalled reading once about bootcamp not trottling down mac the same way as ios does, leading to high temperatures or something.
A quick search got me to this link that in the last post might be related:
Or are you using mac Rhino?